Direct and Regiocontrolled Synthesis of α-Phenyl Ketones from Silyl Enol Ethers and Diphenyliodonium Fluoride

Article abstract of DOI:10.1021/jo00020a013

The efficiacy of diphenyliodonium fluoride (1, DIF) for the phenylation of silyl enol ethers was investigated.When the silyl enol ethers of cyclopentanone, 2-methylcyclopentanone, cyclohexanone, 2-methylcyclohexanone, acetophenone, 2-pentanone, diisopropyl ketone, and pinacolone were mixed with DIF in tetrahydrofuran, either α-phenyl or α,α-diphenyl ketones were produced and isolated in yields ranging from 20 to 88percent.That the regiochemistry of α-phenylation can be controlled by an appropriate choice of silyl enol ether was demonstrated with the kinetic and thermodynamic silyl enol ethers of 2-methylcyclohexanone, the thermodynamic silyl enol ether of 2-methylcyclopentanone, and the kinetic silyl enol ether of 2-pentanone. 3,3-Dimethyl-2-(silyloxy)-1-butene gave a dehydro dimer of pinacolone with DIF in addition to α-phenylpinacolone, thus suggesting that phenylations of silyl enol ethers with DIF may proceed via radical intermediates.